1. Field of the Invention
The present invention relates to a magneto-optical disc recording apparatus for recording information signals upon a magneto-optical disc housed in a cartridge, and in particular to a disc cartridge misinsertion preventing mechanism for preventing a disc cartridge from being misinserted into a cartridge holder which forms a disc cartridge loading mechanism for loading the disc cartridge into a disc loading portion provided in a recording apparatus, the apparatus including a mechanism for controlling the movement of an external magnetic field generator toward and away from the disc in association with the commencement and stopping of the rotation of the magneto-optical disc loaded in the disc loading portion.
2. Related Art Statement
Magneto-optical discs including a signal recording layer in which so called perpendicular magnetization is possible have been proposed. In order to record information signals on the magneto-optical disc, an area of the signal recording layer on which information signals are recorded is heated to a temperature not less than Curie temperature by focusing a laser beam on the signal recording layer and the laser beam thereto and an external magnetic field is applied to this area.
Since the signal recording layer which has been heated to a temperature not less than the Curie temperature substantially loses its coercive force, the magnetization direction of the molecules is reversed along the line of the external magnetic field. By reversing the magnetization direction of the signal recording layer in such a manner, recording of digitalized information signals can be performed.
A magneto-optical disc recording apparatus which writes information signals on such a magneto-optical disc, comprises a rotary driving device which holds and rotates the magneto-optical disc, an optical pick-up device for irradiating the signal recording layer of the magneto-optical disc with a laser beam and an external magnetic field generator which applies an external magnetic field upon the signal recording layer.
In the above mentioned magneto-optical disc recording apparatus, some external magnetic field generators include a so-called flying magnetic head. The flying magnetic head is biased in such a direction that it is moved toward a rotating magneto-optical disc. The flying magnetic head comprises a core and a coil which is wound and housed in the core for generating a magnetic field. The core of the flying magnetic head is formed in such manner that the head is moved in close to the magneto-optical disc to form a very small air gap therebetween so that air entrained between the core and the rotating magneto-optical disc forms an air film.
The core of such a flying magnetic head is finished to a smooth planar face on the side of the head facing the magneto-optical disc to form on effective air film because, if the flying magnetic head is brought into contact with the magneto-optical disc while the disc is stationary, there is the possibility that the magneto-optical disc and the flying magnetic head would be damaged.
In the above mentioned disc recording apparatus, some external magnetic field generators are supported by a rotatable arm so that they are movable toward and away from the disc.
In such a magneto-optical disc recording apparatus, it is necessary to rotate the arm over a sufficient angle to separate the external magnetic field generator from the disc by such a distance that loading, unloading and eject operation of the disc may be performed. If the rotating angle of the arm is increased, the apparatus becomes complicated in structure and miniaturization of the apparatus becomes difficult.
If a magneto-optical disc housed in the cartridge is used in the magneto-optical disc recording apparatus in which the external magnetic field generator is supported on the rotatable arm as mentioned above, there is the possibility that the arm will contact the edge of the cartridge when the external magnetic field generator is moved sufficiently close to the disc. If the arm is brought into contact with the edge of the cartridge, the quality of recording of information signals is substantially reduced.
The disc cartridge which houses the magneto-optical disc and is used for this type of magneto-optical disc recording apparatus is formed as shown in FIGS. 1 and 2.
The disc cartridge 101 comprises a square main cartridge body 102 which is formed by abutting upper and lower halves 102a and 102b so that they are engaged with each other and a magneto-optical disc 103 which is rotatably housed in the main cartridge body 102 as shown in FIGS. 1 and 2. A magnetic head opening 104 and an optical head opening 105 extend in a lateral direction through the middle of the upper and lower halves 102a and 102b, respectively, which form a main cartridge body 102 in which the magneto-optical disc 103 is housed and is offset to the front side of the main cartridge body 102. A radial part of the signal recording surface of the magneto-optical disc 103 is exposed to the outside through these openings 104 and 105. A magnetic head for generating an external magnetic field and an optical head are disposed within a recording apparatus for recording desired information signals on the disc 103 and face the disc through these openings. The disc cartridge 101 includes an opening 106 into which rests the disc table of a disc rotating drive apparatus provided within the recording apparatus for rotating the magneto-optical disc 103. The opening 106 is located substantially in the center of the lower half 102b so that the opening 106 is continuous with the optical head opening 105.
A shutter 107 which opens and closes each of the openings 104, 105 and 106 is movably mounted on the main cartridge body 102 so that dust and the like will be prevented from penetrating into the main cartridge body 102 through the magnetic head opening 104, the optical head opening 105 and the disc table opening 106 and from contaminating and damaging the signal recording surface of the optical disc 103 housed in the main cartridge body 102. The shutter 107 is formed by bending a thin metal plate into a U-shaped cross-section and is mounted on the main cartridge body 102 from the front side thereof to cover the opening 104, 105 and 106 with a pair of upper and lower covering plates 107a and 107b, respectively. The shutter 107 is biased by a shutter closing spring (not shown) to close the openings 104, 105 and 106 when the disc cartridge is not loaded on the recording and/or playback apparatus and is not used.
The disc cartridge 101 is provided with the magnetic head opening 104 and the optical head opening 105 which the external magnetic field generating magnetic head and the optical head face, respectively in a position offset toward the front side of the main cartridge body 102 as mentioned above. Accordingly, the direction of loading of the disc cartridge 101 with respect to the cartridge loading portion of the recording and/or playback apparatus is determined in order to align the external magnetic field generating head and the optical head with the magnetic head opening 104 and the optical head opening 105.
The disc cartridge 101 is provided with a notch 109 for determining the direction of insertion into the cartridge holder 121 when the disc cartridge 101 is loaded on the cartridge loading portion by using the cartridge loading apparatus having the cartridge holder 12.1 shown in FIGS. 1 and 2. The notch 109 is formed by truncating a corner of the disc cartridge 101 on one side of the cartridge corresponding to the shutter 107 of the main cartridge body 102. The shape of the substantially square disc cartridge 101 will become asymmetric in lateral and longitudinal directions by providing such a truncated corner 109.
The disc cartridge 101 is formed with a recess 110 to which a cartridge gripping mechanism of the cartridge holder is adapted for automatically loading and unloading the cartridge into the cartridge holder. One of the recesses 110 is formed on each side of the main cartridge body 102 near the shutter 107. The recesses 110 are formed so that they extend through the lower half 102b and through a portion of the upper half 102a and terminate at the upper end in the portion of the upper half 102a.
The cartridge holder 121 of the cartridge loading device for loading the thus formed disc cartridge 101 on the cartridge loading portion is formed as shown in FIG. 1. That is, the cartridge holder 121 comprises a main face 122 which is substantially the same size as that of the face of the optical-disc cartridge 101 and cartridge supports 123, 124 provided on the opposite sides of the main face 122. The cartridge supports 123 and 124 are bent in an L shape in cross-section for holding the opposite sides of the main cartridge body 102. A cartridge holding portion 121a comprises an area surrounded by the main face 122 and the cartridge supporting portions 123 and 124. A shutter opening and closing lever 125 is mounted on the cartridge holder 121. The lever 125 is adapted to move the shutter 7 in a direction represented by an arrow A in FIG. 1 against a biasing force of a shutter closing spring 108 (not shown) for opening each of the openings 104, 105 and 106 formed in the main cartridge body 102 when the disc cartridge 101 is inserted. The shutter opening and closing lever 125 has a shutter opening and closing pin 126 provided at the tip end thereof. The shutter opening and closing pin 126 projects downward from the lever 125 to the inside of the cartridge holder 121 through a rotary guide groove 127 bored in the main face 122 of the cartridge holder 121. The lever 125 is pivotally mounted on a pivot shaft 128 erected from the main face 122 of the cartridge holder 121 at the base end thereof so that the lever is rotatable around the pivot shaft 128. The shutter opening and closing lever 125 is biased by a tension spring 129 tentioned between the lever 125 and a misinsertion detecting lever 130 which will be described hereafter so that it is rotated in a direction B represented by an arrow B in FIG. 1. When the disc cartridge 101 is not inserted, the pin 126 of the shutter opening and closing lever 125 is engaged with a stopper piece 127a formed at one end of a rotary guide groove 127 which will oppose a shutter opening and closing pin engaging recess 111 formed in the disc cartridge 101 for restricting the rotary and biasing position of the lever.
The shutter opening and closing pin engaging recess 111 is formed adjacent the shutter 107 and on the side opposite to the side of the main cartridge body 102 at which the notch 109 is formed.
A misinsertion detecting lever 130 is mounted on the cartridge holder 121 in the vicinity of cartridge support 123 for detecting the misinsertion of the disc cartridge 101 to prevent the cartridge holder 121 from being inserted into the inside of the cartridge holder 121 when the disc cartridge 101 is inserted in a wrong direction. The misinsertion detection lever 130 has a misinsertion detection pin 131 projecting downward at the tip end thereof and is mounted at its based on the main face 122 so that it is pivotable around a pivot shaft 132 erected on the main face 122 of the cartridge holder 121. The misinsertion detection pin 131 projects into the inside of the cartridge holder 121 through a notched hole 133 bored from cartridge support 123 to the main face 122. The misinsertion detection lever 130 is biased to rotate in a direction represented by an arrow c in FIG. 1 by a tension spring 129 tensioned between the lever 130 and the shutter opening and closing lever 125. When the disc cartridge 101 is not inserted, the rotating and biasing position of the misinsertion detecting pin 131 is restricted so that the misinsertion detection pin 131 may be engaged with a notch 109 of the disc cartridge 101 to be inserted into the cartridge holder 121. The rotation of the misinsertion detection pin 131 is limited by the engagement of the misinsertion detection pin 131 with the edge of the side of the main face 122 in the notch 133.
The disc cartridge 101 is inserted into the thus formed cartridge holder 121 through the insertion opening at the front side of the cartridge holder 121 while the upper side of the opening 104 for the magnetic head faces the main face 122 of the cartridge holder 121. The front side of the cartridge holder 121 on which the shutter 107 is mounted is a leading end for insertion and the opposite sides of the main cartridge body 102 are engaged with and supported by respective cartridge supports 123 and 124 as shown in FIG. 1. When the disc cartridge 101 is inserted into the cartridge holder 121 properly as shown in FIG. 1, the misinsertion detection pin 131 is brought into an engagement with the notch 109 of the disc cartridge 101. When the disc cartridge 101 is further inserted into the cartridge holder 121 from this position, the misinsertion detection lever 130 having the misinsertion detection pin 131 engaged with the notch 109 is rotated in a direction opposite arrow C in FIG. 1, against the biasing force of the tension spring 129 while the misinsertion detection pin 131 slides along the notch 109 so that the misinsertion detection pin will move to the side of the main cartridge body 102 for enabling the disc cartridge 101 to be inserted to a proper loading position in the cartridge holder 121.
When the disc cartridge 101 is inserted into the inside of the cartridge holder 121 to rotate the misinsertion detection lever 130 as mentioned above, the shutter open and closing pin 126 will be in engagement with the shutter opening and closing pin engagement recess 111 of the disc cartridge 101. When the disc cartridge is further inserted into the cartridge holder 121, the shutter opening and closing lever 125 is rotated in a direction opposite arrow B in FIG. 1 against a biasing force of the tension spring 129 since the shutter opening and closing pin 126 is urged by the disc cartridge 101. The shutter 107 of the disc cartridge 101 is opened by the shutter opening and closing pin 126 against a biasing force of the shutter closing spring 108 (not shown) to move in a direction of arrow A in FIG. 1 for opening each of the openings 104, 105 and 106. When the disc cartridge 101 has been inserted in a predetermined position into the cartridge holder 121, each of the openings 104, 105 and 106 is completely opened.
If the disc cartridge 101 is misinserted from the rear side with respect to the shutter 107, the misinsertion detection pin 131 would abut on and be engaged with the rear side of the disc cartridge since the cartridge 101 is not formed on the rear side thereof with any notch which has been mentioned above. The misinsertion detection lever 130 cannot be rotated, thus preventing the disc cartridge 101 from being inserted into the cartridge holder 121. That is, the misinsertion detection lever 130 prohibits the disc cartridge 101 from being inserted into the cartridge holder 121 unless a notch is formed on the leading corner of the disc.
Some of the disc cartridges housing a disc recording medium are very analogous in shape. For example, a magnetic disc cartridge housing a magnetic disc which is 3.5 inches in diameter is analogous to the disc cartridge 101 housing the above mentioned disc 103. The magnetic disc cartridge 201 is identical to the cartridge 101 in size and structure except that the thickness D.sub.1 of the above mentioned disc cartridge 101 is greater than the thickness D.sub.2 of the magnetic disc cartridge 201. The cartridge 201 is formed as shown in FIGS. 3 and 4. That is, the magnetic disc cartridge 201 comprises upper and lower square halves 202a and 202b which are abutted on and engaged with each other and a magnetic disc 203 rotatably housed therebetween as is similar to the disc cartridge 101. The upper and lower halves 202a and 202b which form the housing body 202 housing the magnetic disc 203 are provided with openings 204 and 205 extending in a lateral direction through the center of the housing and is offset to the front side of the cartridge. A part of the signal recording surface of the magnetic disc 203 is exposed through openings 204 and 205.
A shutter 207 having a U-shaped cross section which opens and closes the openings 204 and 205 is mounted on the cartridge 201 so that it adapted thereto. Thus shutter 207 is biased by a shutter closing spring (not shown) so that the shutter 207 will close the openings 204 and 205 when the magnetic disc cartridge 201 is not loaded on the recording and/or playback apparatus and is not used.
The openings 204 and 205 of the magnetic disc cartridge 201 are also provided in a position offset to the front side of the cartridge 201 through which the signal recording surface of the magnetic disc 203 is exposed as is similar to the disc cartridge 101. In order that the magnetic an optical heads of the recording and/or playback apparatus which move through respective openings 204 and 205 into the cartridge 202 correspond to respective openings 204 and 205, the loading direction of the magnetic disc cartridge 201 on a cartridge portion of the recording and/or playback apparatus must be predetermined. The magnetic disc cartridge 201 is also provided with a notch 209 for determining the direction of insertion of the cartridge into the cartridge holder when the disc cartridge 201 is loaded on the cartridge loading portion of the recording and/or playback apparatus by using a cartridge loading device with the cartridge holder.
Furthermore, the magnetic disc cartridge 201 is also provided with a recess 210 which is to be engaged with the cartridge gripping mechanism of the cartridge holder so that loading and unloading operation of the cartridge on and from the cartridge loading portion of the recording and/or playback apparatus can be automatically performed by the cartridge holder similarly to the disc cartridge 101.
The magnetic disc cartridge 201 is formed substantially identically with the disc cartridge 101 in size on plan and in the notch 209 for misinsertion prevention. Therefore, there is the possibility that the magnetic disc cartridge 201 would be accidentally inserted into the cartridge holder 121 for the disc cartridge 201.
If the magnetic disc cartridge 201 is accidentally inserted into the cartridge holder 121, misinsertion detection pin 131 is urged to the side edge of the magnetic disc cartridge 201 by the notch 209 of the magnetic disc cartridge 201 as shown in FIG. 5 so that the misinsertion detection lever 130 is moved against a biasing force of a tension spring 129 for enabling the magnetic disc cartridge 201 to be inserted.
However, if the magnetic disc cartridge 201 is inserted into the cartridge holder 121 while the notch 209 corresponds to the misinsertion detection lever 130, the lower half 202b would face the main face 122 of the cartridge holder 121 and the edge 210a of the recess 210 would face the misinsertion detection pin 131. Since the misinsertion detection pin 131 comprises a metal pin having a small diameter which extends from the tip end of the misinsertion detection lever 130 and is formed shorter in length than the height (H.sub.1) of the cartridge holder 121, the misinsertion detection pin 131 would be engaged with the recess 210 as shown in FIGS. 5 and 6 to lock the cartridge in place if the cartridge is inserted into the magnetic disc cartridge 201. Once the misinsertion detection pin 131 is engaged with the recess 210, it is difficult to remove the magnetic disc cartridge 201 from the disc holder 121 or further insert the cartridge 201 into the disc holder 121. As a result of this, the magnetic cartridge 201 and the cartridge holder 121 may be damaged.